1. Field of the Invention
The present invention relates to a dischargeable black dyeing of acid modified polyester fibers. More particularly, the present invention relates to a process for dyeing acid modified polyester fibers black, which is partially white or color-dischargeable using a dyeing bath containing a combination of specific dyes.
2. Description of the Prior Art
Polyester fibers have been used widely as a synthetic fiber having excellent physical properties for cloth. However, it has thus far been difficult to ground-dye such fibers black which is partially white or color-dischargeable.
Separately from this, a number of attempts have been made of modify polyester fibers so that they can be dyed with cationic dyes, and one such attempt is disclosed in, for example, Japanese Pat. No. 10,497/1959 in which sulfoisophthalic acid is copolymerized as an acidic material to produce the polyester fiber.
However, when so modified polyester fibers are dyed with a commercially available black cationic dye for polyacrylonitrile fiber, the black dyeings obtained can hardly be discharged. Additionally, when the fibers are dyed black with a combination of dyes which are conventionally used for dischargeable dyeing of acrylic fibers, the black dyeings obtained change in color, on discharge treatment, also in areas other than those to be discharged. Therefore, such a combination of dyes is completely unsuitable for practical use. The reason is as follows. The steaming treatment for discharging black dyeings of acrylic fibers is carried out at a temperature of about 100.degree. to 105.degree.C, on the other hand, the steaming temperature must be increased to about 120.degree. to 130.degree.C for discharging black dyeings of modified polyester fibers. Therefore, easily dischargeable cationic dyes can not withstand this high temperature steaming.